This invention relates to electronic wireless communication devices and, more particularly, to near field communication devices and operating methods therefor.
Near Field Communication or NFC, is a short-range high frequency wireless communication technology which enables the exchange of data between devices over about a 10 cm distance. The communication protocol and operation is an extension of the ISO 14443 proximity-card standard (contactless card, RFID) and is specified in the ECMA-340 and ISO/IEC 18092 technology standards. NFC is used in some devices to combine the interface of a smartcard and a reader into a single device. An NFC device may communicate with both existing ISO 14443 smartcards and readers, as well as with other NFC devices, and is thereby compatible with existing contactless communication infrastructure.
Like ISO 14443, NFC devices communicate via magnetic field induction. Loop antennas in the devices are placed in closed proximity to each other within the other's antenna near field, thereby effectively forming an air-core transformer. NFC devices typically transmit within the globally available and unlicensed radio frequency ISM band of 13.56 MHz, with a bandwidth of almost 2 MHz. NFC devices also typically support data rates of 106, 212, or 424 kbit/s using a modified Miller coding or Manchester coding to encode and decode communicated data.
NFC devices can be configured to operate in either a passive or an active communication mode. When operating in the passive communication mode, the initiator device provides a carrier field and the target device answers by modulating the carrier field. In this mode, the target device may generate its operating power from the initiator-provided electromagnetic field, thus making the target device a transponder. In contrast, when operating in the active communication mode, both the initiator device and the target device communicate by alternately generating their own RF fields when communicating, and by deactivating their own RF field while waiting for data from the other device. Accordingly, when operating in the active communication mode, both devices typically need to have their own power supply.